Shark Repellant

We revisit scientific research that will help us better understand these extraordinary creatures. Graham Phillips discovers how understanding a sharks' sensory system could help people swim safely amongst the carnivorous fish.This story was originally broadcast in May 2012 but new research results from the University of Western Australia can be found in the Further Info section.

TRANSCRIPT

NARRATIONImagine coming face to face with a great white shark. Brian Sierakowski doesn't need to imagine.

Brian SierakowskiThat's where the shark attack occurred.

Dr Graham PhillipsSo you've got to look at the very spot every morning.

Brian SierakowskiEvery morning, yeah.

NARRATIONBack in 1997, he was having his morning surf ski.

Brian SierakowskiWhen the shark came up, his whole jaw consumed the whole front of my ski in front of my toes. So I was thrown into the water and there was the shark looking at me, his face was right at me with the ski in his mouth.

NARRATIONBrian lived to tell the tale... ..but another attack on the same beach a few years later killed Ken Crew. Indeed, just in the south-west of Australia, in only the last year, four people have lost their lives to sharks.

Dr Graham PhillipsIs there a way of developing some kind of repellent to protect people from sharks? Well, researchers here at the University of Western Australia think there might be, but to do it, they must first understand how sharks see and sense the world.

NARRATIONSharks see much like us.

Professor Shaun CollinThe design of the eye is almost the same as the design of our eyes.

NARRATIONBut there's a key difference. Researchers discovered it by studying these guys - small Port Jackson sharks. They're bottom-dwellers and can grow up to a metre and a half long. They're in the waters all round Southern Australia. This guy's been given a general anaesthetic.

Dr Graham PhillipsWhat's the tube for?

Associate Professor Nathan HartBecause they're anaesthetised, their breathing slows down. So we need to make sure that they're getting oxygenated water over their gills, as well as the anaesthetic to keep them asleep.

Dr Graham PhillipsHe looks pretty still now.

Associate Professor Nathan HartYes, that's right. The anaesthetic's working, so we got the electrodes in and a fibre-optic pointing at the eye there, which is going to flash the lights onto his eye.

NARRATIONBy flashing different frequency light onto the eye, Nathan can work out which colours the shark can detect. And the surprise was sharks only see in black and white and that gave an important clue for developing a shark repellent.

Professor Shaun CollinIf they're not using colour, it appears that they are more interested in contrast rather than colour. Contrast, of course, can be a silhouette against the backlight of the sun if the animal's moving towards prey from below.

NARRATIONToday's black wetsuits are definitely high contrast. Perhaps we could do better by creating a wetsuit with a blue-green colour like water or a reflective suit. The researchers are going to investigate. Vision, however, is not the only sense. This Port Jackson will be given a hearing test. It's out of the tank and into a bath of anaesthetic. He slowly drifts off. Then it's off to the testing tank. An underwater speaker plays a variety of sounds to the shark, and electrodes are attached to its head.

Dr Brandon CasperThis actually records the signals from the brain in response to the different sounds we play. What we're looking for is evidence the shark is actually hearing the sounds we're playing to it. So we play sounds - for example, a 200 hertz sound, and then we actually look for a similar signal coming back from the shark's brain, suggesting it's actually detecting these signals.

NARRATIONBy playing tones of different frequency and volume, we can find out just what a shark hears.

Dr Brandon CasperTheir most sensitive hearing is at the lowest frequencies, so this 70 hertz, 100 hertz, really up to around 200 hertz.

NARRATIONIn nature, these are the frequencies sharks are interested in. They're emitted by their dinner - swimming fish. But researchers have found artificial sounds attract their attention too.

Dr Brandon CasperThey were playing really loud, low-frequency pulsed sounds and they would find that the sharks would be attracted, potentially from hundreds of metres away.

NARRATIONTraditional fishermen know too. Sharks can be attracted from great instances with special rattles. But the task at hand is not about attracting sharks.

Professor Shaun CollinBut maybe, in doing this, we could in fact develop other sounds that they may be repelled from.

Dr Brandon CasperOh, it's certainly possible there could be some sounds that they might find to be really obnoxious, that might get them to leave the area.

NARRATIONA tantalising possibility for a shark repellent and the researchers plan to investigate it. But what about that sense sharks have, that we don't?

Professor Shaun CollinThey're able to detect very, very weak electric fields in the water, down in the nanovolt range. So this is very, very minute.

NARRATIONSharks have a series of jelly-filled pores under the surface of their skin. They're those black dots. They measure voltage differences, allowing the sharks to detect electric fields. In fact, for this sense, there's already shark protection on the market - the Shark Shield.

Dr Graham PhillipsThe idea is you just velcro this to your ankle and the antenna streams out behind you, as you swim. Now, it generates a very intense electric field, in fact, way stronger than the shark would ever experience in the wild. So when the shark approaches, it says, 'Whoa! What's that?' and heads in the other direction.

NARRATIONThe makers of the product have done some limited testing and it certainly repels some sharks sometimes.

Professor Shaun CollinBut the Shark Shield isn't necessarily set at a level that may disturb all of the different shark species because we know very little about the detection thresholds of many different species.

Ryan KempsterI was actually told that people wearing Shark Shields were in fact followed by Port Jackson sharks when they had the device active. This suggested to me that obviously this device wasn't working as a repellent, as it should be. It was actually working as some form of attractant.

NARRATIONAttracting sharks?! You don't want to hear that. Ryan decided to investigate. There are electrodes hidden in this Perspex square.

Ryan KempsterThrough this, we can control the electric field that's produced, that comes out of this sheet in the bottom of the tank. This way, we can actually watch from a camera above and monitor the sharks as to how they are actually attracted or indeed repelled by given electric fields.

NARRATIONSure enough, for certain fields, the sharks were indeed attracted. Of course, Port Jacksons aren't man-eaters but learning about sharks in general will help us understand the dangerous ones as well. But check out another species - bamboo sharks. They hatch from eggs and that gave the researchers an idea. They could test electric fields on sharks that couldn't swim away. The breathing shark is clearly visible inside the egg but then the field is switched on.

Ryan KempsterWe actually found our embryos would actually completely stop all their body movements, and completely stop breathing while they were stimulated with a specific kind of electric field from 15 to about 45 seconds, while the stimulus was going on. As soon as we took away the stimulus, they would start breathing again.

NARRATIONSo for bamboo sharks, it's the opposite of Port Jacksons. They're scared of electric fields - a protection mechanism against predators. So, while there certainly is the potential to develop a shark repellent, it's not going to be a simple task. We may even have to attack multiple senses at the same time.

Associate Professor Nathan HartI don't think it's going to be a question of a single device. Sharks are very complex animals. They have a battery of senses and obviously are going to need a range of different strategies to prevent an attack.

NARRATIONIn the meantime, the advice is just put sharks out of your mind, keep swimming.

Professor Shaun CollinI certainly would. Chances of getting taken by a shark are extremely remote.

Ryan KempsterI dive, I swim, I surf, you know. I'm happy in the water.